Group net interest margin for the three months ended Sept. 30 was lower due to higher funding costs, CBA said in a limited trading update, without giving a number. Last year, it had disclosed unaudited first-quarter cash profit of A$2.4 billion.

Troublesome and impaired assets for the September quarter increased slightly to A$6.8 billion due to ongoing stress in the New Zealand dairy sector but fell slightly as a proportion of loans, CBA said.

Australian bank returns have been under pressure from higher wholesale funding and deposit costs, as well as regulatory changes requiring them to hold more capital against their mortgage books to provide a more level playing field for smaller banks. ($1 = 1.2953 Australian dollars) (Reporting by Jamie Freed; Editing by Louise Ireland)